SIP Trunk reregistration failing

[Dercni]

I have an on-prem 3CX server that uses one SIP provider for inbound calls and another for outbound calls.

Periodically the SIP trunks appear to attempt to reregister.

The Inbound SIP trunks reregister without a problem however the outbound trunks fail to register. The following error is shown for each outbound SIP trunk that fails to reregister:

Registration at Outbound Line 2 has failed. Destination (sip:*.*.*.*:5060;transport=TCP;lr) is not reachable, DNS error resolving FQDN, or service is not available.

If I restart the SIP service all trunks reregister and work perfectly.

Any suggestions as to what may be causing this, how I may diagnose it further or implement a workaround?

 

[leejor]

Have you tried changing your DNS server? As a test, before making any changes, try using the IP address of the provider, in the trunk settings, rather than the FQDN, see if that makes a difference.